Air bag arrangement

ABSTRACT

In an air-bag arrangement in a motor vehicle a gas generator ( 5 ) has a flange ( 8 ) which is spaced from a flange member ( 3 ) by elongate spacer elements ( 9 ). The spacer elements pass through apertures ( 20, 21 ) formed in an air-bag adjacent a central aperture ( 19 ). On inflation of the air-bag, the part of the air-bag surrounding the aperture will be drawn into an engagement with the flange ( 8 ). Should a very high pressure exist within the air-bag, the part of the air-bag surrounding the aperture will be driven away from the flange ( 8 ), with part of the aperture sliding along the elongate elements ( 9 ), thus permitting excess pressure to be relieved.

[0001] THE PRESENT INVENTION relates to an air-bag arrangement for amotor vehicle and more particularly relates to an air-bag arrangementsuitable for mounting in front of an occupant of the motor vehicle inthe steering column or the dashboard of the vehicle.

[0002] It is known to mount an air-bag and a gas generator arrangementin front of an occupant of the motor vehicle such that in an accidentsituation, the gas generator will inject gas into the air-bag to inflatethe air-bag. Thus, as the torso and head of the occupant move forwardrapidly, the inflated air-bag provides a cushioning effect to reduce orminimise injury to the occupant of the vehicle.

[0003] However, a problem arises with such prior air-bag arrangementswhen the occupant of the vehicle is not fully sitting back in thevehicle seat. For example the occupant of the vehicle may be leaningforward to obtain an item from the glove compartment or may, for anyother reason, be sitting forwardly of the seat such that his head andupper torso is relatively close to the air-bag arrangement.

[0004] If an occupant of the vehicle is leaning forwardly relative tothe normal position of an occupant of the seat, the rapidly inflatingair-bag will impact with the occupant and further inflation of theair-bag will be resisted or prevented. Consequently the gas pressurewithin the air-bag will increase to a level much greater than thatexperienced during unimpeded inflation of the air-bag. Consequently highforces will be exerted on the part of the occupant adjacent the air-bag,which may lead to serious injuries. It is therefore desirable, afterpart of the occupant has impacted with the air-bag, to reduce gaspressure within the air-bag and consequently to reduce the force exertedby the inflating air-bag on the part of the occupant of the vehicle.

[0005] The present invention seeks to provide an improved air-bagarrangement.

[0006] According to the present invention there is provided an air-bagarrangement for a motor vehicle comprising an air-bag, a gas generatorhaving a flange member and an apertured base plate member spaced apredetermined distance away from the flange member, elongate elementsbeing provided extending between the flange member and the base platemember, the air-bag having an opening forming a throat, the air-bag alsohaving a plurality of apertures surrounding said opening, each aperturereceiving a respective said elongate element the arrangement being suchthat, in an accident situation, as gas from the gas generator isintroduced to the air-bag, a part of the air-bag adjacent the openingmoves into substantially sealing engagement with the flange member ofthe gas generator and such that, if the inflating air-bag impacts withan occupant of the vehicle, increasing gas pressure within the air-bagmoves the part of the air-bag surrounding the opening towards the baseplate member so that gas flows from the air-bag through a gas flow pathdefined at least partly by the space between the flange member and thebase plate member.

[0007] Preferably the elongate elements comprise elongate studs eachhaving a large diameter region inserted through a respective aperture inthe air-bag, and a smaller diameter terminal region inserted in anaperture formed in the base plate member. Each stud serves as a spacerbetween the flange member and the base plate member.

[0008] Conveniently each stud is provided with a screw thread on which anut is secured.

[0009] In one embodiment the elongate elements comprise studs and eachstud passes through a bush which serves as a spacer between the flangemember and the base plate member.

[0010] Alternatively the elongate elements comprise tabs which extendfrom one member to the other member.

[0011] Alternatively the elongate elements comprise protrusionsextending from one member to the other, the protrusions serving asspacers between the flange member and the base plate member.

[0012] Preferably each protrusion defines an aperture through which arespective stud is inserted.

[0013] Preferably the throat is dimensioned to receive part of the gasgenerator.

[0014] Conveniently the throat is reinforced with an additional layer ofmaterial.

[0015] Advantageously the additional layer of material is formed of afabric.

[0016] Alternatively the additional layer of material is formed ofmetal.

[0017] Alternatively the additional layer of material is formed of aplastics material.

[0018] In order that the invention may be more readily understood, andso that further features thereof may be appreciated, the invention willnow be described, by way of example, with reference to the accompanyingdrawings in which:

[0019]FIG. 1 is an exploded perspective view of the air-bag arrangementof the current invention;

[0020]FIG. 2 is a sectional view of the air-bag arrangement taken online A-A of FIG. 1 showing the air-bag arrangement in a first condition;and

[0021]FIG. 3 is a sectional view corresponding to FIG. 2 but showing theair-bag arrangement in a second condition.

[0022] An air-bag arrangement 1 comprises a gas generator 2, a baseplate member 3 and an air-bag 4.

[0023] The gas generator 2 comprises a cylindrical housing comprising anupper circular end 5 and a lower circular end 6 interconnected by atubular side wall 7. A substantially square flange member 8 extendsradially from and surrounds the tubular side wall 7 and separates thefirst circular end 5 from the second circular end 6. The flange member 8is provided with four elongate elements in the form of studs 9 which aresubstantially equispaced about the flange member 8. The studs 9 extendfrom the side of the flange member 8 closest to the second circular end6 in a direction parallel to the tubular side wall 7 of the gasgenerator 2.

[0024] Each stud 9 has two regions of different diameter. The region 10of each stud 9 closest to the flange member 8 has a relatively largediameter and the region 11 of each stud 9 remote from the flange member8 has a relatively small diameter. The small diameter region 11 isprovided with a screw thread.

[0025] Four tabs 12 also extend from the side of the flange member 8closest to the second circular end 6 in a direction parallel to thetubular side wall 7. Two tabs 12 are located on one part of the flangemember 8 between two of the studs 9 and the other two tabs 12 arelocated on an opposing part of the flange member between the other twostuds 9.

[0026] The base plate member 3 comprises a substantially square plate ofuniform thickness. The base plate member 3 has a centrally locatedcircular aperture 13 dimensioned to receive the second circular end 6 ofthe gas generator 2. The upper surface of the base plate member 3extends around the circular aperture 13 and is provided with fourprotrusions 14 which extend upwardly and substantially perpendicularlyfrom the upper surface of the base plate member 3. Each protrusion 14 isprovided with an axial bore 15 which extends through the protrusion 14and through the base plate member 3. Each bore 15 is dimensioned andlocated to receive the smaller diameter region 11 of a respective stud9. The upper surface of the base plate member 3 is also provided withfour recesses 16 each dimensioned and located to receive a lower portionof a respective tab 12.

[0027] The air-bag 4 comprises two fabric layers 17 and 18, each fabriclayer 17 and 18 comprising a circular disc of fabric. The layers offabric 17 and 18 are superimposed and are connected at theirperipheries, for example by a seam. The lower fabric layer 17 isprovided with a centrally located circular opening 19 forming a throat.The circular opening 19 is dimensioned and located to receive the lowercircular end 6 of the gas generator 2. Four apertures 20 are formed inthe first fabric layer 17 and are equispaced about the periphery of theopening 19. The four apertures 20 are dimensioned and located such thatboth regions 10 and 11 of each stud 9 may be inserted through arespective aperture 20. Four further apertures 21 are also providedabout the periphery of the opening 19 and are dimensioned and locatedsuch that part of each tab 12 may be inserted through a respectivefurther aperture 21.

[0028] In assembling the air-bag arrangement, the gas generator 2 willbe inserted through the opening 19 of the first fabric layer 17 so thatthe gas generator 2 is located within the interior of the air-bag 4. Thegas generator 2 will be aligned with the first fabric layer 17 such thateach stud 9 will be inserted through a respective aperture 20 of thefirst fabric layer 17 and such that each tab 12 will be inserted througha respective further aperture 21 of the first fabric layer 17. Thesecond circular end 6 of the gas generator 2 may protrude through theopening 19 in the air-bag 4.

[0029] The gas generator 2 and the air-bag 4 will then be offered to thebase plate member 3, the base plate member 3 being orientated such thatthe smaller diameter region 11 of each stud 9 may be inserted through arespective bore 15 on the base plate member 3. It is to be appreciatedthat, when so inserted, part of the smaller diameter region 11 of eachstud 9 will extend beneath the lower surface of the base plate member 3and a nut 22 will be screwed onto the screw thread provided on therespective lower region 11 of the respective stud 9. Each tab 12 will bereceived within a respective recess 16 on the base plate member 3. Thusthe first fabric layer 17 of the air-bag 4 will be sandwiched betweenthe flange member 8 of the gas generator 2 and the base plate member 3.It is to be appreciated that the larger diameter region 10 of each stud9 will space the flange member 8 of the gas generator 2 a predetermineddistance from the base plate member 3. It is also be appreciated thatthe tabs 12 will also assist in spacing the flange member 8 of the gasgenerator 2 and the base plate member 3 the same predetermined distanceapart. It is envisaged that the predetermined distance apart will bebetween 2 millimetres and 10 millimetres.

[0030] It is to be further appreciated that, when the above arrangementis assembled as has been described, the apertures 20 and furtherapertures 21 provided around the periphery of the opening 19 of thefabric layer 17 of the air-bag 4 are permitted to slide along the studs9 and the tabs 12 respectively. Thus the part of the first fabric layer17 of the air-bag 4 adjacent to the opening 19 may move from a positionadjacent the flange member 8 of the gas generator 2 to a positionadjacent the base plate member 3.

[0031] Referring now to FIG. 2, in an accident situation, gas will beinjected from the gas generator 2 into the air-bag 4 in a directionsubstantially as shown by arrow 23. This direction of flow of gas fromthe gas generator 2 will give the entire air-bag momentum in thedirection shown by the arrow 23 and the first fabric layer 17 will bemoved along the studs 9 and tabs 12 to a position adjacent and firmly incontact with the flange member 8 of the gas generator 2. It is to beappreciated that when the fabric layer 17 of the air-bag 4 is in thisposition, the air-bag 4 is substantially sealed and gas from the gasgenerator 2 will remain substantially in the air-bag 4. Thus the air-bagwill inflate in a conventional manner.

[0032] If an occupant of the vehicle is leaning forwardly of the vehicleseat and is thus relatively close to the inflating air-bag 4, theinflating air-bag 4 will impact with part of the occupant of the vehicleprior to the air-bag 4 being fully inflated. Further inflation of theair-bag 4 in the direction of the arrow 23 in FIG. 2 will be preventedor restricted and thus gas pressure within the air-bag 4 will increase.The increasing gas pressure within the air-bag 4 will move the part ofthe air-bag 4 adjacent the opening 19 away from sealing engagement withthe flange member 8 of the gas generator 2 to a position adjacent baseplate member 3. This movement will be enabled by the apertures 20 andfurther apertures 21 sliding along the larger diameter region 10 of thestuds 9 and along the tabs 12 receptively. This is the position shown inFIG. 3.

[0033] When the part of the fabric layer 17 adjacent the opening 19 isin the position shown in FIG. 3, it is to be appreciated that gas mayflow from the air-bag through a gas flow path defined by the spacebetween the flange member 8 of the gas generator 2 and the base platemember 3, the opening 19 in the air-bag 4 and the aperture 13 in thebase plate member 3. This gas flow path is shown by arrows 24. This flowof gas from the air-bag will reduce the gas pressure within the air-bag4 and thus the force exerted by the inflating air- bag 4 on the part ofthe occupant of the vehicle in contact with the air-bag 4 will beregulated. It is envisaged that this regulation of force will greatlyreduce the risk of injuries being imparted to the occupant by theinflating air-bag 4.

[0034] It is to be appreciated that, in an alternative embodiment, thespacing between the flange member 8 of the gas generator 2 and the baseplate member 3 may be effected solely by the studs 9, with the tabs 12being omitted, or solely by the tabs 12, with the studs being of uniformsection along their length. The tabs may be on the base plate member 3instead of being on the flange member 8.

[0035] In a further alternative embodiment each stud 9 comprises astandard bolt of constant diameter which is inserted in a bush prior tobeing secured to the base plate member 3. The bushes serve to space thegas generator 2 and the base plate member 3 the predetermined distanceapart.

[0036] In a further alternative embodiment, each protrusion 14 serves asa spacer between the flange member 8 and the base plate member 3. Eachstud 9 comprises a standard bolt of constant diameter which is insertedin a respective aperture 15 formed in each protrusion 14. When assembledas has been described above, the part of the fabric layer 17 which formsthe periphery of each aperture 20 is clamped between the flange member 8and a respective protrusion 14. Thus, in an accident situation, the partof the air-bag between each protrusion 14 in an accident situation willmove from a position adjacent the flange member 8 to a position adjacentthe base plate member 3 to allow gas to flow out of the air-bag.

[0037] Further, it is envisaged that the periphery of the opening 19forming the throat of the first fabric layer 17 could be reinforced withan additional layer of material. Such a material could be formed from afabric, a plastic or a metal material.

[0038] In the present Specification “comprises” means “includes orconsists of” and “comprising” means “including or consisting of”.

1. An air-bag arrangement for a motor vehicle comprising an air-bag, agas generator having a flange member and an apertured base plate memberspaced a predetermined distance away from the flange member, elongateelements being provided extending between the flange member and the baseplate member, the air-bag having an opening forming a throat, theair-bag also having a plurality of apertures surrounding said opening,each aperture receiving a respective said elongate element, thearrangement being such that, in an accident situation, as gas from thegas generator is introduced to the air-bag, a part of the air-bagsurrounding the opening moves into substantially sealing engagement withthe flange member of the gas generator and such that, if the inflatingair-bag impacts with an occupant of the vehicle, increasing gas pressurewithin the air-bag moves the part of the air-bag surrounding the openingtowards the base plate member so that gas flows from the air-bag througha gas flow path defined at least partly by the space between the flangemember and the base plate member.
 2. The arrangement of claim 1 whereinthe elongate elements comprise elongate studs each having a largediameter region inserted through a respective aperture in the air-bag,and a smaller diameter terminal region inserted in an aperture formed inthe base plate member.
 3. The arrangement of claim 1 or claim 2 whereineach stud is provided with a screw thread on which a nut is secured. 4.The arrangement of any one of the preceding claims wherein the elongateelements comprise studs and wherein each stud passes through a bushwhich serves as a spacer between the flange member and the base platemember.
 5. The arrangement of any one of the preceding claims whereinthe elongate elements comprise tabs which extend from one member to theother member.
 6. The arrangement of any one of the preceding claimswherein the elongate elements comprise protrusions extending from onemember to the other, the protrusions serving as spacers between theflange member and the base plate member.
 7. The arrangement of claim 2wherein each protrusion defines an aperture through which a respectivestud is inserted.
 8. The arrangement of any one of the preceding claimswherein the throat is dimensioned to receive part of the gas generator.9. The arrangement of any one of the preceding claims wherein the throatis reinforced with an additional layer of material.
 10. The arrangementof claim 9 wherein the additional layer of material is formed of afabric.
 11. The arrangement of claim 9 wherein the additional layer ofmaterial is formed of metal.
 12. The arrangement of claim 9 wherein theadditional layer of material is formed of a plastics material.